This invention relates to electronic packaging and assembly devices, including inter alia ball grid array packaging (BGA), chip size/scale packaging (CSP) and multi-chip-module/packaging (MCP/MCM), passive electrical devices, and a process of manufacturing therefor. In addition, the invention relates to a fixture for masking purposes.
Microelectronic devices are typically manufactured from a brittle semiconductor material which requires protection from moisture and mechanical damage as provided for: by an electronic package which also contains electrically conductive traces to connect between a semiconductor device and external circuitry.
Depending on the intended complexity of an electronic package, a multi-layer interconnect structure can be interposed between one or more integrated circuit chips (ICCs) and a substrate (PCB). One such multi-layer interconnection structure is illustrated and described in U.S. Pat. No. 5,661,341 to Neftin and includes aluminum layers, each layer typically having a thickness of several micrometers and being deposited on a previously prepared topside of an underlying layer.
Another package design which minimizes space requirements and provides a high density of interconnections between circuit chips and external circuitry is a Ball Grid Array (BGA) packages Different types of BGA packages have been described in that art and include a metal based BGA package as illustrated and described in WO 94/22168 to Mahulikar and a plastic based BGA package as illustrated and described in U.S. Pat. No. 5,355,283 to Marrs R. C. et al. U.S. Pat. No. 5,045,921 to Lin P. T. et al. In the former type, a metallic base contains a plurality of electrical conductive vias which are electrically isolated from the base have opposite ends respectively electrically connected to external circuitry and an integrated circuit device. The process for manufacturing such a BGA package includes drilling holes in the metal base, anodizing the metal base and inserting metal pins into the insulated holes. Such a metal based BGA package has good thermal performance. In the latter type, an organic material is used to form dielectric layers of a multi-layered substrate having vias formed by mechanical or laser drilling and into which are inserted electrically conductive material. This BGA type package has low thermal performance and facilitates a relatively high interconnection density capability.
BGA packages have now been developed with improved heat dissipation from the heat producing dies. Particular implementations are illustrated and described inter alia in U.S. Pat. Nos. 5,583,778 and 5,629,835.
Conventional masking for area selective anodization purposes is a relatively complicated and expensive process including the application and subsequent removal of an inert masking layer using photolithography and deposition techniques. A masking layer can be in the form of photoresist material, a dense oxide layer, a tantalum metal thin film, and the like. In U.S. Pat. No. 5,661,341, there is described the use of a photoresist mask. In WO 95/08841, there is described the use a dense oxide mask. In JP 1,180,998, there is described the use of rubber mask. In JP 54,0332,279, there is described the use of a metal mask. In JP 59,094,438, there is described the use of a photoresist mask in an anodization process.
In accordance with a first aspect of the present invention, there is provided a device comprising a discrete solid body having a pair of opposing generally parallel major surfaces, said solid body having a body portion of a porous valve metal oxide based material with a pair of exterior surfaces respectively constituting portions of said major surfaces and extending inward from one said major surface towards the other said major surface, said body portion having one or more electrically insulated valve metal conductive traces of from about 10 xcexcm to about 400 xcexcm thickness in a direction from one said major surface to the other major surface embedded therein, one or more of said traces having a trace portion divergingly extending inward from an exterior surface constituting a portion of one of said major surfaces.
Porous anodization penetrates an original valve metal blank at a slightly higher rate in the direction of a voltage difference across its opposing major surfaces than in a transverse direction thereto such that a circular masking element on one of a valve metal blank""s major surfaces effectively protects an inwardly directed diverging cone shaped valve metal via during a so-called one-sided porous anodization of the blank. In a similar manner, a pair of circular masking elements applied to both of a blank""s major surfaces in registration to one another such that their centers are concentric effectively protect a barrel shaped valve metal via during a so-called two-sided porous anodization. One-sided porous anodization can typically anodize a valve metal blank to a maximum porous oxide thickness of about 200 xcexcm relative to one of its opposing major surfaces whilst two-sided porous anodization can typically anodize a valve metal blank to a maximum porous oxide thickness of about 400 xcexcm thereby delimiting the thickness of an electrically insulated valve metal conductive trace from about 10 xcexcm to about 400 xcexcm thickness.
A device of the present invention can be fabricated from suitable valve metal blanks of aluminum, titanium, tantalum, and other valve metals and preferably include inter alia Al 5052, Al 5083, Al 5086, Al 1100, Al 1145, and the like. A device of the present invention can be readily manufactured to customer requirements in terms of a desired product specification including inter alia electrical properties; thermo-mechanical properties such as thermal coefficient of expansion (TCE), Young modulus, elasticity; thermal properties such as thermal conductivity coefficient; and other factors. A device of the present invention has good thermal performance, facilitates high interconnection density capability and can. be manufactured by a low cost, simple, environmental friendly process.
Each device can be considered as being constituted by different combinations of evo or more types of basic building blocks extending between a device""s opposing major surfaces. The building blocks include a full original valve metal building block, a full porous oxide building block, a composite porous oxide on original valve metal building block, a composite original valve metal on porous oxide building block and a sandwich porous oxide on original valve metal on porous oxide building block. A wide range of devices of the present invention are envisaged including inter alia a Ball Grid Array (BGA) support structure, a Multi-Chip Module (MCM) support structure, a Chip Scale Package (CSP) support structure for connecting IC devices or devices and electronic boards typically printed circuit boards (PCBs), an interconnect device for interconnection purposes, a coil for coil and transformer applications, and others.
In accordance with a second aspect of the present invention, there is provided a process for manufacturing a device having a desired product specification, the process comprising the steps of:
(a) providing a discrete valve metal blank having a pair of opposing generally parallel major surfaces;
(b) selectively masking at least one of the major surfaces of the blank in accordance with the desired product specification; and
(c) porously anodizing the selectively masked blank for converting a body portion thereof into porous valve metal oxide and having a pair of exterior surfaces respectively constituting portions of the major surfaces and extending inward from one major surface to the other major surface, the body portion having one or more electrically insulated valve metal conductive traces of from about 10 xcexcm to about 400 xcexcm thickness in a direction from one major surface to the other major surface embedded therein, one or more of the traces having a trace portion divergingly extending inward from an exterior surface constituting a portion of one of the major surfaces.
The process of the present invention can manufacture a device with a relatively simple product specification with a single porous oxide thicknesses with respect to either one of the blank""s opposing major surfaces from a valve metal blank by a single one-sided porous anodization or both of the blank""s opposing major surfaces by a single dual-sided porous anodization. In addition, the process of the present invention can manufacture a device with a relatively complicated product specification with two or more different porous oxide thicknesses in respect of one or both of the blank""s opposing major surfaces. Such different porous oxide thicknesses can be achieved either by two or more consecutive porous anodizations each with different masking or, alternatively, by a single porous anodization with masking applied to the blank""s opposing major surfaces for protecting different areas thereof against porous anodization for different lengths of time.
Different time delay protection can be achieved by dense oxide masking elements (hereinafter referred to as DOMEs) of different thicknesses which are themselves converted to porous oxide during porous anodization. However, conversion of dense oxide occurs at a far slower rate than the conversion of original valve metal material such that, for example, a 0.1 xcexcm thick DOM protects underlying original valve metal material for about 3 hours during which time one-sided porous anodization can normally convert original valve metal material to porous oxide to thickness of 40 xcexcm. The process of the present invention can also employ a composite mask including a photoresist mask on a relatively thick DOM, for example, 0.5 xcexcm, so as to effectively block porous anodization of original valve metal material under the DOM.
The process of manufacturing devices in accordance with the present invention is suitable for large area panel production containing a plurality of devices.
During or post porous anodization, suitable substances can be impregnated into a blank""s porous oxide portions in order to seal its pores, for example, as described in U.S. Pat. No. 3,622,473 to Toshiyuki et. al. In addition, a blank typically thickens during porous anodization such that it requires planarization to a desired degree of planarity and to arrive at a desired thickness for the BGA, MCM, CSP support structures, and the like.
In accordance with a third aspect of the present invention, there is provided a pin jig fixture for use with an electrical power source for porous anodization of a valve metal blank having a surface, the pin jig fixture comprising a bed of pins each having a leading end surface for intimate juxtaposition against the surface for masking a corresponding area thereof, one or more of said leading end surfaces being directly connected to the electrical power source for electrically connecting the electrical power source to the surface on intimate juxtaposition thereagainst.
A pin jig fixture in accordance with the present invention enables the simultaneous masking of one or more areas of a surface of a valve metal blank by its mechanical clamping thereagainst and the electrical connection to an electrical power source for porous anodization of the blank. Thus, the pin jig fixture advantageously negates the need for an otherwise redundant portion of a valve metal blank which is conventionally initially used for connection to an electrical power source and which is subsequently removed.